The present invention relates to disc storage systems. More specifically, the present invention relates to a buffer memory for a disc storage system.
Disc storage systems, such as magnetic or optical disc storage systems, are used to store information for subsequent retrieval. The speed at which information can be written to or read from the disc is determined by a number of physical constraints. For example, if the transducer which is used to write information to or read information from the disc surface is positioned over one area of the disc and data needs to be written to or read from another area of the disc, the transducer must be physically moved between annular data tracks across the disc surface. Further, as the disc rotates, the write or read operation may be delayed until the disc rotates to the proper position.
The delay in writing information to, or reading information from a disc surface can introduce delays in a host computer when writing to or reading from the disc storage system. For example, the host computer must wait for the disc storage system to complete the write or read operation. One technique for reducing this waiting time is to add a cache or buffer memory to the host computer or the disc storage system.
When the host computer initiates a data write operation for example, the data is first written to the buffer memory. After the data has been written to the buffer, the host computer can continue with subsequent operations and is not required to wait until the write operation is complete. The data is removed from the buffer as it is needed by the disc and when it can be written onto the disc surface.
Buffer memories also capitalize on the characteristic that once a host computer reads data from or writes data to disc drives, it is very likely that this data will be reused by the host computer in the near future. Thus, frequently used data or instructions are replicated in buffer memories.
Retrieving data from the buffer memory avoids the necessity of accessing one or more discs of the disc drive which are relatively slow compared to the buffer memory. Therefore, data retrieval is accomplished more rapidly which, in turn, leads to an overall increase in system performance.
As mentioned above, caching techniques can be implemented in the host computer or the disc storage system. There are a number of problems with caching techniques implemented in the host computer. These techniques take processing time from the host computer to manage the buffer. Further, since the host computer is responsible for storing the data, data can still be lost at the disc drive level. In addition, these techniques usually require the host computer to be specially configured.
Conventional caching techniques employed in disc storage systems typically utilize dynamic random access memory (DRAM) devices. DRAM cells are fast and expend little power, but have to be refreshed many times each second and require complex structures to incorporate a capacitor in each cell. Further, DRAM cells are xe2x80x9cvolatilexe2x80x9d in the sense that upon power-down, the memory contents are lost.
The present invention addresses these problems and offers other advantages over the prior art.
The present invention relates to a disc storage system employing a non-volatile magnetoresistive random access memory (MRAM) buffer, thereby addressing the above-identified problems.
In accordance with one embodiment, the present invention includes a disc storage system having a host computer interface adapted to couple to a host computer, a disc storage medium having a disc surface and a spindle motor coupled to the disc adapted to rotate the disc. A transducer is positioned for reading and writing data on the disc surface. The system further includes a non-volatile MRAM buffer adapted to temporarily store data during read and write operations and to preserve stored data during a power loss to the disc storage system.
Another embodiment relates to a method of caching data in a disc storage system. The method includes temporarily storing data in a non-volatile MRAM buffer during read and write operations. The method further includes preserving data stored in the non-volatile MRAM buffer during a power loss to the storage system.
These and various other features as well as advantages which characterize embodiments of the present invention will be apparent upon reading of the following detailed description and review of the associated drawings.